1. Field of the Invention
The present invention relates to a safety valve mechanism which is thermally activatable and has particular utility in operations relating to offshore oil and gas wells.
2. Description of the Prior Art
During the drilling, completion and production of an off-shore oil and gas well, it has been prudent practice recently to utilize safety valve mechanisms which are fluid operational to shift the head of the valve mechanism to a position to isolate the well in the event of a blowout or other catastrophe. Many of these valve mechanisms are hydraulically activatable, the hydraulic fluid being hydrocarbonbased and thus flammable. The valves are maintained in normal open position by pressure within the hydraulic control line extending from the valve and/or actuator for the valve immediate the well to an hydraulic control panel or console on the rig platform or other structure. In the event of a blowout, pressure within the control line is held off and the valves are manipulated to closed position. The distance from the control panel to the valve or actuator mechanism oftentimes can be several hundred feet. Since the hydraulic fluid itself is highly flammable, the fluid within the control line will be of considerable volume and could act as additional fuel for a fire, even during a bleedoff at the control panel or other point. It would thus be desirable to provide a means for reducing this additional source of fuel for the fire resulting from a blowout or other catastrophe around a well or platform or the like.
The present invention provides such means whereby an apparatus is located along the transmission line between the control panel and the valve actuator or valve assembly whereby the apparatus is thermally activatable to close off and isolate the fluid transmission line from the apparatus to the control panel from the transmission line downstream of the apparatus to the actuator or valve mechanism. Additionally, the present apparatus permits fluid in the transmission line downstream of the apparatus to be dumped through the apparatus so that hydraulic fluid may be transmitted away from a potential source of fire, i.e., the well area. Additionally, the apparatus of the present invention provides a timing assembly which is pre-settable to isolate the fluid transmission line downstream of the apparatus from the dumping means after dumping of the hydraulic fluid has been completed.